This research will be done in Argentina in collaboration with Dr. Guillermo Lanuza as an extension of the NIH/NINDS grant 5 R37 NS037075-09. Functional Analysis of Inhibitory Spinal Cord Interneurons (8/15/2006-3/31/2010). Recent studies in the developing spinal cord have led to a model in which neurons are initially determined by unique genetic programs controlled by the combinatorial action of transcription factors expressed in dorsoventrally restricted populations of precursors. In spite of the considerable progress made in understanding early events in cell fate specification, the mechanisms that lead to the specification and generation of mature neuronal cell types in the adult remain to be elucidated. In this research proposal we will address the diversification of embryonic V2b interneurons of the spinal cord and brainstem in at least two different subsets: a) inhibitory neurons that extend axons ipsilaterally and b) neurons that contact the cerebrospinal fluid (CSF) in the central canal. We will study the development of CSF- contacting neurons and ask whether they constitute a late-born population of V2b neurons. We will define the genetic program that specifies generic V2b or V2b subtype identity by focusing on the role that the transcription factors Foxn4 and Mash1 play in V2b precursors. In addition we will test our hypothesis that Gata2 and Gata3 control the differentiation of CFS-contacting neurons. Finally, we will determine the function in vivo of central canal neurons. Their role as chemosensors and regulators of homeostasis of the internal fluid will be assessed in experiments using genetic ablation approaches to probe their function. PUBLIC HEALTH RELEVANCE: These studies will yield a better understanding of the mechanisms that underlie neuronal diversification in the spinal cord and the brainstem. More importantly, they will lay the groundwork for strategies to treat spinal cord injury, degenerative disorders and respiratory dysfunctions.